Hydrazine, acetate (1:1) → 2,3-di-O-acetyl-4,6-dichloro-4,6-dideoxy-D-galactopyranose

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A solution of acetyl 2,3-di-O-acetyl-4,6-dichloro-4,6-dideoxy-D-galactopyranose (compound 82) (2.24 g, 6.5 mmol) and hydrazine acetate (903 mg) in DMF (22 mL) was stirred for 2 hours at room temperature. The reaction mixture was then diluted with dichloromethane (250 mL) and washed 4 times with water (4×250 mL), dried over anhydrous sodium sulfate and evaporated. Flash chromatography using hexane-ethyl acetate (1:1) as an eluent gave 2,3-di-O-acetyl-4,6-dichloro-4,6-dideoxy-D-galactopyranose (~6.88 mmol). This compound was then dissolved in dichloromethane (20 mL) cooled to 0° C., and trichloroacetonitrile (3.35 mL, 34.4 mmol) was added. After stirring at 0° C. for 40 minutes, the solvent was evaporated and the residue was chromatographed on a silica gel column, eluting with hexane-ethyl acetate (5:1), to give imidate 83 (1.14 g, 39%) as a white solid.

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